Method for producing rectangular shaped synchronizing impulses



May30,1939. J. SCHUNACK. 2,160,522

METHOD FOR PRODUCING RECTANGULAR SHAPED SYNGHRONIZING IMPULSES Filed D99. 11, 1936 swam kw w wwa Patented May 30, 1939 UNITED STATES Berlin-Charlottenburg, Gerassignor to the firm of Fernseh Aktiengesellschaft, Zehlendorf, near Berlin, Ger- Johannes Schunack,

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Application December 11, 1936, Serial No. 115,415 In Germany January 14, 1936 3 Claims.

The present invention relates to a method for producing synchronizing signals for television transmission purposes and deals more particularly with the production of rectangular shaped 5 impulses of short duration.

It is known that impulses of such short duration can be produced from sinusoidal impulses e. g. with the aid of an over-modulated tube or with the aid of an iron choke operating in the saturation range.

The method of the present invention likewise uses an over-saturated iron choke but in a new, particularly advantageous arrangement. In order to produce only voltage peaks of one and the same polarity at the iron choke and to use them for modulation, the anode current of a tube is used, in accordance with the present invention, for saturating the iron choke, and this current is so adjusted that at normal anode current the 2. choke is just saturated.

The method will be explained in connection with an embodiment and the accompanying drawing. In this embodiment a self-excited oscillation of a feed-back tube is used as the modulating sinusoidal oscillation. However, in lieu of the self-oscillating tube a sinusoidal modulating oscillation may be fed to the grid of the tube. The feed-back tube I preferably has a weakly damped grid circuit and a large internal resistance. A screen grid tube may be used, for example, wherein the screen grid as indicated by the dotted lines, is connected with a tap-off point of the battery 5. An iron choke 2 is disposed in the anode circuit of tube l. The natural frequency of this choke is preferablyequal to or greater than the fundamental frequency of the excitation oscillation. The choke is preferably wound in 'a non-capacitative manner in order to achieve a large alternating resistance. For

example, the well known pancake (wafer) type of winding may be used. Another tube 3 may, for example, be connected to the choke. The grid resistance 4 of this tube is preferably made large so as to obtain a short impulse of as powerful a nature as possible and of exact rectangular shape from the impulses taken off from the choke. To the same end, the tube 3 may also have a strong negative static potential.

The tube l produces practically sinusoidally shaped oscillations at the grid independently of the nature of the anode circuit. These oscillations are converted by the iron choke 2 into impulses of short duration and of but single polarity and fed to the next tube 3,

56 signal is received, allows an anode current to which, when a PATENT- OFFIC pass corresponding to the polarity of the voltage impulse. A short synchronizing impulse of exactly rectangular shape may be taken off from the resistance 6 if the resistance 4 is sufliciently large, e. g. l megohm. 5

Such a method requires only one choke for converting the sinusoidal oscillation and, if desired, one further tube, for producing the rectangular form of the impulse. The expenditure required for such a circuit is therefore very small in contrast with the heretofore usual arrangements in which a plurality of tubes was always used. The method may be used both at the transmitting as well as at the receiving end. 15 The arrangement of a self-excited tube isof advantage, for example, in the modulation of image scanning tubes.

I claim:

Means for generating synchronizing impulses of rectangular waveform comprising an electron discharge device having an input and an output circuit, means for applying an alternating potential of substantially sinusoidal waveform to said input circuit, a source of direct current voltage and an iron cored choke serially connected in said output circuit, said output circuit having a normal direct current component of current therethrough of a value to saturate said iron cored choke, a second electron discharge device having an output circuit including 0 an impedance, and means for overmodulating said second electron discharge device with voltage pulses derived from across said source of direct current potential and said iron cored choke in series, whereby across said impedance will be developed voltage impulses of substantially rectangular waveform.

2. Means for generating synchronizing impulses of rectangular waveform comprising an 40 electron discharge device having an input and an output circuit, means for applying an alternating potential of substantially sinusoidal waveform to said input circuit, a source of direct current voltage and an iron cored choke con- 45 nected in said output circuit, said output circuit having a normal direct current component ofcurrent therethrough of a value to saturate said iron cored choke, a second electron discharge device having an output circuit including a re- 50 sistance, and means for overmodulating said second electron discharge device with voltage pulses derived from across said source of direct current potential and said iron cored choke, whereby across said resistance will be developed voltage impulses of substantially rectangular waveform.

3. Means for generating synchronizing impulses of rectangular waveform comprising a source of oscillations having an output circuit including a direct current voltage source and an iron cored choke in series therewith, said output circuit having a direct current component of current sufficient to saturate said iron cored w choke, an electron discharge device having an output circuit including a resistance and means for overmodulating said electron discharge device with impulses developed across said direct current source and said iron cored choke in series therewith during operation of said source of oscillations whereby voltage impulses of rectangular waveshape will be formed across said resistor.

J OHANNES SCHUNACK. 

